Whenever, i try to start up Complete, the screen turns black and you hear the computer warming up, like it always does. However, the screen turns back to the windows screen and the start-up stops. I just uninstalled regular CIV III to free up some space on my computer. Is it because of this?

Thanks

Maybe. Try unintalling Complete as well, the reinstalling it.

would reinstalling it reset the high scores and such?

Not sure. If in doubt, back up any .cv3 or .hof files.